Write protection should not vary between debug and prod mode

[alunny]

Discussed briefly with @PhUU and mentioned to @lawnsea.

Right now the canWriteProtect function in utils behaves different in debug mode from production/normal mode:
https://github.com/flightjs/flight/blob/master/lib/utils.js#L12

If debug.enabled is true, mixins cannot overwrite functions from earlier mixins. Otherwise, later mixins clobber functions from earlier mixins.

This can lead to nasty bugs where a component will behave differently when debugging from production mode.

I'd like to remove the setWritability calls entirely from compose.mixin, since that's how the library behaves in production. The alternative way to eliminate the discrepancy would be to always write protect, which is much slower.

Thoughts?

[angus-c]

If clobbering is detected in debug mode doesn't it throw an error? If it does than I think that's fine. If it doesn't then it should.

[alunny]

Nope, writing to a non-writable property does not throw an error. It just fails silently.

> foo = {}
{}
> foo.bar = 'hello'
'hello'
> Object.defineProperty(foo, 'bar', { writable: false })
{ bar: 'hello' }
> foo.bar = 'goodbye'
'goodbye'
> foo.bar
'hello'

[angus-c]

We should make it error (it used to). Unless no-one cares about clobbering (but they probably should)

[alunny]

It looks like this behavior's been the same since the first open source commit, at least.

[angus-c]

yeah you right, idk.

[giuseppeg]

weird it should throw in strict mode

[alunny]

(long delayed response).

weird it should throw in strict mode

Yeah my mistake, I was running the node repl in sloppy mode.

That said, flight cannot control whether the code that uses it runs in strict mode or sloppy mode. So I think the problem is still valid.